package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSON;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author YJY
 * @since 2025-03-10
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;
    @Override
    public Result queryById(Long id) {
        //缓存穿透
        Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);
                //id2->getById(id2) k可以写成this::getById
//        Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);
//        if(shop==null){
//            return Result.fail("商铺不存在!");
//        }

        //逻辑过期方式解决缓存击穿问题
//        Shop shop = queryWithLogicalExpire(id);

        return Result.ok(shop);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.存在,直接返回
            return null;
        }
        //4.命中 需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期 直接返回店铺信息
            return shop;
        }
        //5.2 已过期需要缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2 判断获取锁成功
        if (isLock) { //注意:注意获取锁成功应该再次检测redis缓存是否存在,做DoubleCheck如果存在无需重建缓存.
            //6.3 成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }

            });
        }
        //6.4 返回过期的商铺信息
        return shop;
    }

    //缓存穿透
    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在,直接返回
            return JSONUtil.toBean(shopJson, Shop.class);

        }
        //判断命中的是否是空值
        if (shopJson != null) {
            //返回一个错误信息
            return null;

        }
        // 4.开始实现缓存重建
        // 4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        Shop shop = null;
        try {
            // 4.2判断是否获取成功
            if (!isLock) {
                // 4.3失败 则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }

            // 4.4成功,根据id查询数据库  注意获取锁成功应该再次检测redis缓存是否存在,做DoubleCheck如果存在无需重建缓存.

            shop = getById(id);
            //模拟重建的延时
            Thread.sleep(200);
            //5.不存在,返回错误
            if (shop == null) {
                //将控制写入Redis 解决缓存穿透问题
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //6.存在,写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unlock(lockKey);

        }
        //8.返回
        return shop;
    }

      @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        String key = CACHE_SHOP_KEY + id;
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(key);
        return Result.ok();
    }

    //Redis中的setnx 来模拟互斥锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        //不要直接返回flag 它会做一个自动拆箱可能会产生空指针
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    public void saveShop2Redis(Long id, Long expireSeconds) {
        //1.查询店铺数据
        Shop shop = getById(id);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入Redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }


    //缓存穿透
    public Shop queryWithPassThrough(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在,直接返回
            return JSONUtil.toBean(shopJson, Shop.class);

        }
        //判断命中的是否是空值
        if (shopJson != null) {
            //返回一个错误信息
            return null;

        }
        //4.不存在,根据id查询数据库
        Shop shop = getById(id);
        //5.不存在,返回错误
        if (shop == null) {
            //将控制写入Redis 解决缓存穿透问题
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在,写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }
}

